1. FIELD OF THE INVENTION
The present invention relates to a controller for a printer for printing bit images according to data input from an external data processor such as a host computer.
2. DESCRIPTION OF PRIOR ART
Generally, data fed from an external data processor such as a host computer etc. include printing data representing an actual printing pattern and control data for controlling a printing method and a mode of a print engine of the printer. A controller for the printer processes the data by transforming them into dot images or bit map images to be actually printed out and sends them to the print engine.
Recently, with increasingly high performance of printers, the technical specification of the control data has been extremely complicated. Therefore, a relatively long time is needed for processing the print data by the controller. No great improvement in the processing speed of a CPU for controlling the controller can be expected because of the limitation of the performance of the hard-ware thereof, resulting in that it is difficult to provide a printer which is able to process the print data at a higher speed. Therefore, even though a print engine having a higher printing speed is used, the efficiency of the data processing can not be improved.
In order to improve the through-put of the printer system, there is provided a method for transforming data of pages subsequent to the page in printing into intermediate codes, by calculating print addresses and analyzing protocols such as a font selection and the like beforehand. However, it is impossible to alter a size or a direction of a copy paper with respect to data having been already transformed into intermediate codes even if they are not printed yet.
The present invention is intended to overcome the aforementioned disadvantages by interrupting the processing for printing and reanalyzing the data when the command for altering the paper size or the printing direction, is entered from the printer.
In the case of the aforementioned reanalysis of the data, if a protocol for outputting a response data to the external data processor is included in the data to be reanalyzed, the response data is outputted to the external data processor during reanalyzing of the data, resulting in a trouble caused in the external data processor.